Conventional premolded housings have unstructured and smooth housing bottoms. To install stress-sensitive (micromechanical) sensor chips in such a housing, isolating it from all possible types of stress, soft adhesives, for example silicone adhesives, are often used. However, such adhesives have the disadvantage under certain conditions that they have insufficient adhesion to the currently used premolded housing materials, such as LCP. Thus, at high temperatures, for example, the sensor chip may become detached from the housing bottom, resulting in damage to the sensor chip or in incorrect measurements.
German Patent Application No. DE 198 29 248 describes extrusion of a plastic body onto a printed circuit sheet whose printed circuits have a “cauliflower” structure having depressions and projections. The extrusion produces, together with the increasing cross section of the printed circuits, a form-fitting rigid bond between the plastic body and the printed circuit sheet.
Another possibility of securing a sensor chip in a premolded housing is to cover the sensor chip fully or partially with a (passivating) gel as shown, for example, in German Patent Application No. DE 102 004 015 123.